DC systems offer many advantages over AC systems, such as a higher flexibility of power management, a higher performance, a better reconfigurability and power-flow controllability. Despite these advantages, common disturbances for DC systems, such as short circuits, power outages, and voltage sags, are major concerns for DC systems. Short circuits in DC systems are more dangerous and difficult to extinguish than in AC systems, because of their potentially higher currents. Voltage sags can also cause severe problems in DC systems. When voltage sags occur, constant power loads can cause a negative incremental impedance instability that can lead to system failure if not compensated. Cascading effect between short circuits and negative incremental impedance instabilities is another problem for DC systems. For example, a short circuit fault in one distribution line can induce voltage sags and cause negative incremental impedance instabilities in other circuits within a same zone. Thus, there is a need for more sophisticated methods and systems for protecting DC circuits.